The general, long term objective of this application is to study the mechanisms that contribute to cell-specific regulation of cytochrome P-450 isozyme function and expression. Cytochromes P-450 are a superfamily of enzymes catalyzing a large number of bioactivation and detoxication reactions with xenobiotics as substrates, as well as critical steps in steroid biosynthesis with endogenous substrates. Hence these enzymes play critical roles both as cellular defense mechanisms and mediators of essential steroid biosynthesis. Bioactivation of xenobiotics to toxic reactive intermediates is frequently a determinant of tissue-selective toxicity or carcinogenicity. This project seeks to develop an improved understanding of the mechanisms regulating the expression (induction and suppression) and function of individual members of this family of enzymes. This project will focus on mechanisms conferring cell-specific patterns of function and expression, which consequently produce cell-specific metabolic capacities which in turn result in tissue-selective bioactivation or detoxication patterns. The overall goal of the proposed project is to determine the molecular mechanisms by which a series of model compounds [n- alkylmethylenedioxy-benzenes (MDBs), analogs of many naturally occurring plant compounds], selectively regulate cytochromes P-450 in a cell-specific manner. Regulatory mechanisms of P-450 isozyme expression and function will be studied and compared between liver and lung by Western blotting, in vitro metabolism studies, immunocytochemistry, Northern blotting and solution hybridization with synthetic cDNA oligonucleotide probes. These studies will be conducted employing a combination of in vivo and in vitro model systems, including intact tissues, microsomes, and viable populations of specific cell types grown in culture or purified by centrifugal elutriation. A new protein believed to be a previously unreported P-450 isozyme, induced only by specific longer chain synthetic MDBs, will be purified and investigated at the molecular level.